Solvent extraction of petroleum



June 16 1942. d 2,286,852

SOLVENT EXTRACTION 0F PETROLEUM Filed Sept. 16, 1938 RAFFINATE MfLV/N M.HOLM INVENTOR ATTORNEY Patented June 16, 1942 2,286,852 SOLVENTEXTRACTION or PETROLEUM Melvin M. Holm, San Francisco, Calif., assignorto Standard Oil Company of California, San Francisco, Calif., acorporation of Delaware Application September 16, 1938, Serial No.230,229

16 Claims.

This invention relates to refining hydrocarbon oil and more particularlyto the extraction of mineral oil fractions, such as petroleum naphtha ormineral lubricating oils, by solvent treatment.

The invention contemplates the treatment and refinement of mineral oilwith a selective solvent liquid to separate therefrom desired orundesired constituents. It contemplates particularly the treatment oflubricating oil to produce therefrom lubricating oil products of desiredcharacteristics. It also contemplates the extraction of lower boilingpetroleum fractions, such as petroleum naphtha, to effect a refinementthereof and/or to separate a fraction of a desired chemical type.

The drawing comprises a diagrammatic flow sheet of one method ofeffecting solvent extraction with the selective solvent of thisinvention.

The invention involves selective solvent extraction of mineral oil witha solvent comprising an amine containing more atoms of carbon than ofnitrogen in its molecule and belonging to the group of such compoundswhich can be formed by the interaction of ethylene dichloride withammonia followed by liberation of free amine by treatment with caustic.The term polyethylene amines is used herein to designate these types of'compounds.

The selective solvent of the process is, in general, either an openchain compound of the general formula NH2.C2H4(C2H4.NH).NH2, where a: isa whole number, or a ring compound having the general formulaoH.NH)aozmuH:

where :L' is a whole number. The first group is exemplified bydiethylene triamine (NH2.C2H4.NH.C2H4.NH2)

triethylene tetramine (NH2.C2H4.NI-I.C2H4.NH.C2H4.NI-Iz) andtetraethylene pentamine (NI-I2.C2H4.NH.C2H4.NH.C2H4.NH.C2H4.NH2)

Examples of the second group are diethylene diamine.

NH NH C2H and triethylene triamine NH Cg C1114 NHCiHiNH Thus thisinvention broadly embraces the use of a selective solvent comprising apolyethylene amine containing more carbon atoms than nitro-,

gen atoms and further characterized by the presence of the chemicalgroupLubricating oils derived from mixed base crudes contain relativelyparaffinic constituents as well as relatively non-paraffinicconstituents including naphthenic, aromatic and unsaturated hydrocarbonbodies. The polyethylene amines above mentioned are particularly Welladapted to the treatment of mineral lubricating oil fractions to effectseparation between the parafiinic and relatively non-parafinicconstituents. Accordingly, the solvent liquids'of the invention areadapted to remove relatively non-parafiinic constituents fromlubricating oil and produce therefrom lubricating oil products of moreparafiinic character and having a higher viscosity index.

In the application of the invention to the treatment of mineral oil forthe production of lubricating oil, one part of the oil is mixed withfrom about one-half to about three or more parts of the solvent liquid.This mixture is then subjected to agitation at a suitable temperature,as for example, about 32 F. to 300 F., and then separated into anextract phase'and a raffinate phase. The extract phase comprises thenonparaifinic constituents of the oil dissolved in the solvent liquid,while the raffinate phase comprises the relatively paraifinicconstituents of the oil.

The two phases are separated from each other and the solvent removedtherefrom by distillation or by washing with another suitable solventliquid.

The extent to which the oil is soluble in the solvent depends upon thenature of the oil as well as the temperature of extraction and the ratioof solvent liquid to oil employed during extraction. The extractiontemperature and the ratio of solvent to oil may be Varied for thepurpose of efiecting the particular degree of extraction desired.Consequently, in some instances, it may be desired to employtemperatures either somewhat below or somewhat higher than thosementioned above, and likewise the ratio of solvent to oil may be eithergreater or less than that specified.

As a specific example, a lubricating oil comprising a heavy distillatefrom a California (Midway) crude and having the tests indicated belowwas extracted with triethylene tetramine. The oil was extracted withabout 100% by volume of the solvent at a temperature of about F. Themixture was separated into extract and rafiinate phases and theraflinate phase, upon removal of the solvent liquid, comprised about 83%of the original charge.

The tests on the oil before extraction and on the resulting rafiinateand extract oils were as follows:

As previously pointed out, the invention also contemplates theseparation of petroleum naphthas into fractions of difierent chemicaltype. One particular utility for this species of the invention comprisesthe production of low aniline point thinners, that is, fractions of higharomatic content, from petroleum naphthas. These low aniline pointthinners are highly desirable for use in paint compositions and whereverpetroleum fractions with high solvent power are sought. This aspect ofthe invention may also be utilized to extract undesired constituents,such as sulfur, from naphthas to give a raffinate of decreased sulfurcontent.

As a specific example of this species of the invention, a fraction of adehydrogenated naphtha from a Kettleman fields crude, having a boilingrange of 200 F. to 300 F. was extracted with 100 volume per cent oftriethylene tetramine in a one stage batch treatment. The contacting andseparation of the layers were ef fected at approximately 70 F. Therafiinate and extracted oil fractions were freed of associated solventin an ordinary distillation system. Since the end boiling points of therespective oil fractions were much lower than the boiling point of thesolvent, substantially complete vaporization of the rafiinate oil andthe extract oil were effected without vaporization of the solvent. Thismode of operation is highly advantageous because it is only necessary tovaporize one volume of oil in total raflinate and. extract for theseveral s g Rafiinate Extract Volume percent yield 100 83 17 Gravity, A.P. I 54. 4 56. 4 47. 7 Weight percent sulfur 0. 01 0. ll Aniline point99 109 48 It will be observed that the raffinate obtained in the aboveexample is of higher gravity and the extract has a lower aniline pointthan the original naphtha. Subsequent refining treatments may be giveneither the raffinate or extract fraction if further refinement isrequired for particular purposes. Among such additional treatments aresulfuric acid treatment, contact with adsorbent earths and the like.Similarly, the lubricating oil may be subjected to the foregoingextraction treatment with polyethylene amines either before or afterdewaxing, and also either before or after treatment with other solventsor chemicals.

A second example of a method of treating pctroleum naphthas withpolyethylene amine selective solvents to refine the same and/or preparelow aniline point thinners comprises a process wherein the normallyliquid petroleum fraction is countercurrently contacted with theselective solvent at a temperature above the initial boiling point ofthe hydrocarbons being treated. Such a process is illustrated by theflow sheet of the drawing in which the petroleum stock to be treatedpasses from storage hrough valve controlled line H3, heat exchanger I I,line l2, heat exchanger l3, line I l, vaporizer i5, and line [6 to asingle extraction tower ll. The liquid phase selective solventcomprising a polyethylene amine, such as triethylene tetramine togetherwith its dissolved extract, flows from .the bottom of tower ll throughline Hi to vaporizer IS. A portion only of the extract is flashed intovapor form and recirculated through line 28 to tower ll. Solvent iscontinuously removed from vaporizer l9 through line 21 and passed tostill 22 for removal of the extracted hydrocarbons. The extract isseparated from the solvent in fractionating column 23 and flows throughline 24, heat exchanger I3, line 25, and condenser 25 to storage. Theselective solvent is continuously removed from the still andrecirculated to extraction tower I! through valve controlled line 21.The liquid level in Vaporizers l5, l9 and 22 is maintained above theconduit connections I4, l8, 2i and 21 to produce a liquid seal andprevent the flow of vapors through these conduits. Railinate vapors flowfrom the top of extraction tower [1, through line 28 to heat exchanger Hwhere partial condensation occurs. As much of this partial condensate asis desired may be returned to the extraction tower through line 30,controlled by valve 3i. The remainder of the raffinate passes throughcondenser 29 to storage. Valve controlled conduit 32 provides means forsupplying additional condensate to the reflux line when the desiredreflux ratio is higher than that obtainable with the partial condensatealone.

In a single stage extraction process, such as that involved in thedrawing, it is essential that the vapor phase hydrocarbons and theliquid phase selective solvent be intimately contacted. One eflicientmeans for effecting this result comprises the conventional bubble capfractionating column in which the vapors thereby extracted rise upwardlythrough a series of bubble caps and are thereby intimately mixed withthe downflowing selective solvent. Such an extraction tower is thepreferred form but other types of towers may be utilized, for example,packed towers containing Raschig rings, broken quartz and the like.

The type of process illustrated in the drawing is particularlyapplicable to the separation of aromatic hydrocarbons from petroleumfractions and is effective to obtain a sharp separation of hydrocarbonfractions having a boiling range in the order of 100 F. or more andcontaining parafiinic hydrocarbons having a boiling point as much asfrom 20 F. to 60 F. above the boiling point of the aromatics beingextracted. It will be observed that this process is characterized by itsability to separate components of a complex mixture, such as a petroleumnaphtha containing and consisting essentially of aromatic, cyclicnon-benzenoid, and paraflinic hydrocarbon compounds having overlappingboiling ranges by passing said hydrocarbons through an extraction zoneat a temperature above the initial boiling point of the mixture butbelow the end boilin oint thereof whereby a vapor phase is formed,countercurrently extracting these vapor phase hydrocarbons with apolyethylene amine selective solvent maintained in liquid phase but at atemperature above the initial boiling point of the hydrocarbon mixturein the extraction zone and separating a vapor phase rafiinate and aliquid phase extract from the extraction zone.

'I'riethylene tetramine is a selective solvent which has markedstability at high temperatures. Tests have established thatdecomposition of this solvent was less than 0.1% in eight hours at 340F, This property, together with the fact that polyethylene aminesolvents are not corrosive and are not caustic in nature, renders thesesolvents particularly useful for selective solvent processes operated atelevated temperatures.

The various extractions disclosed hereinabove may be carried out in acontinuous countercurrent type of operation or in an intermittent batchtype of operation. In the continuous countercurrent type of operation,the ratio of oil to sol-- vent may be somewhat less than that used inthe batch type of operation.

In some instances it may be of advantage to carry out the extraction inthe presence of a modifying solvent liquid, such as aniline and xylidineor other solvents Which are selective in themselves, or with diluents,such as benzene, toluene, the carbitols and other non-selectivesolvents, or with anti-solvents for the oil, such as water, methylalcohol, ethyl alcohol, glycerol and the like.

Although certain specific amounts of solvent, temperatures, conditionsand sequences of operation and proportions of solvent to oil have beenexemplified above in detail, it is to be understood that all suchamounts, proportions, conditions and sequences are merely illustrativeand are not to be considered as limiting. Numerous changes andmodifications therein can be made, as will be apparent to those skilledin the art, according to the character both of the oils to be refinedand the results sought to be accomplished, and all such changes andmodifications as come within the scope of the appended claims areembraced by the invention.

I claim:

1. In the refining of petroleum oils, the method which comprises mixingthe oil with a selective solvent comprising a polyethylene amine, saidpolyethylene amine molecule having more atoms of carbon than of nitrogenand being further characterized by the presence of the chemical groupforming an extract phase containing a portion of said petroleum oildissolved in the solvent and a raflinate phase comprising undissolvedoil, and separating the two phases.

2. In the refining of petroleum oils, the method which comprises mixingthe oil with a selective solvent comprising an amine having the generalformula where :13 represents a whole number, forming an extract phaseand a raflinate phase, and separating the two phases.

3. In the refining of petroleum oils, the method which comprises mixingthe oil with a selective solvent comprising an amine having the generalformula where x represents a Whole number, forming an extract phase anda raflinate phase, and separating the two phases.

4. In the refining of petroleum oils, the method which comprises mixingthe oil with a selective solvent comprising triethylene tetramine,forming an extract phase and a rafiinate phase, and separating the twophases.

5. In the refining of mineral lubricating oil containing relativelyparafiinic and relatively non-paraflinic constituents, to separatetherefrom a parafiinic fraction of relatively high viscosity index, themethod which comprises mixing the oil with a selective solventcomprising a polyethylene amine, said polyethylene amine molecule havingmore atoms of carbon than of nitrogen and being further characterized bythe presence of the chemical group i r r r-r-r-rr- H H H H H forming anextract phase containing relatively non-parafiinic constituents of theoil dissolved in the solvent liquid and a rafiinate phase comprising therelatively parafiinic constituents of the oil, separating the twophases, and removing the solvent liquid therefrom.

6. In the refining of mineral lubricating oil containing relativelyparaffinic and relatively non-parafiinic constituents, to separatetherefrom a paraffinic fraction of relatively high viscosity index, themethod which comprises mixing the oil with a selective solventcomprising an amine having the general formula Where n: represents awhole number, forming an extract phase containing relativelynon-paraffinic constituents of the oil dissolved in the solvent liquidand a rafilnate phase comprising the relatively parafi'inic constituentsof the oil, separating the two phases, and removing the solvent liquidtherefrom.

7. In the refining of mineral lubricating oil containing relativelyparaffinic and relatively non-parafiinic constituents, to separatetherefrom a parafiinic fraction of relatively high viscosity index, themethod which comprises mixing the oil with a selective solventcomprising an amine having the general formula where :1: represents awhole number, forming an extract phase containing relativelynon-paraffinic constituents of the oil dissolved in the solvent liquidand a raffinate phase comprising the relatively paraflinic constituentsof the oil, sep-. arating the two phases, and removing the solventliquid therefrom.

8. In the refining of mineral lubricating oil containing relativelyparafiinic and relatively non-paraifinic constituents, to separatetherefrom a paraffinic fraction of relatively high viscosity index, themethod which comprises mixing the oil with a selective solventcomprising triethylene tetramine, forming an extract phase containingrelatively non-paraffinic constituents of the oil disolved in thesolvent liquid and a raflinate phase comprising the relativelyparaffinic constituents of the oil, separating the two phases, andremoving the solvent liquid therefrom.

9. In the refining of a normally liquid low boiling petroleum oilcontaining parafiinic and aromatic constituents, to separate therefrom arelatively aromatic fraction of high solvent power, the method whichcomprises mixing the oil with a selective solvent comprising apolyethylene amine, said polyethylene amine molecule having more atomsof carbon than .of nitrogen and being further characterized by thepresence of the chemical group forming an extract phase containingrelatively,

aromatic constituents of the petroleum dissolved in the solvent liquidand a rafilnate phase comprising the relatively paraflinic constituentsof the oil, separating the two phases, and removing the dissolvedhydrocarbons from said extract.

10. In the refining of a normally liquid low boiling petroleum oilcontaining paraffinic and aromatic constituents, to separate therefrom arelatively aromatic fraction of high solvent power, the method whichcomprises mixing the oil with a selective solvent comprising an aminehaving the general formula where :t represents a whole number, formingan extract phase containing relatively aromatic constituents of thepetroleum dissolved in the solvent liquid and a raflinate phasecomprising the relatively paraffinic constituents of the .oil,separating the two phases, and removing the dissolved hydrocarbons fromsaid extract.

12. In the refining of a normally liquid low boiling .petroleum .oilcontaining paraffinic and aromatic constituents, to separate therefrom arelatively aromatic fraction of high solvent power, the method whichcomprises mixing the oil with a selective solvent comprising triethylenetetramine, forming an extract phase containing relatively aromaticconstituents of the petroleum dissolved in the solvent liquid and araflinate phase comprising the relatively paraffinic constituents of theoil, separating the two phases, and removing the dissolved hydrocarbonsfrom said extract.

13. A process of separating components of a complex mixture containingand consisting essentially of aromatic, cyclic non-benzenoid, andparafiinic hydrocarbon compounds having overlapping boiling ranges whichcomprises passing said hydrocarbons through an extraction zone at atemperature above the initial boiling point of the mixture whereby avapor phase is formed, countercurrently extracting said vapor phasehydrocarbons with a selective solvent comprising a polyethylene aminehaving more atoms of carbon than of nitrogen maintained in a liquidphase but at a temperature above the initial boiling point of saidhydrocarbon mixture, separating a vapor phase rafiinate comprising themore paraflinic portion of said original complex mixture,.separatingfrom said extraction zone a liquid phase extract comprising the morearomatic portion of said complex mixture and separating the extractedhydrocarbons from said polyethylene amine.

14. A process as defined in claim 13 in which said polyethylene amine istriethylene tetramine.

15. A process as defined in claim 13 in which said polyethylene amine isan amine having the general formula NH2.C2H4. (C2H4.NH) 9:.NI'I2 where:1: represents a whole number.

16. A process as defined in claim 13 in which the polyethylene amine isan amine having a general formula where m represents a Whole number.

MELVIN M. HOLM.

